The present invention relates to an exit door lock and more particularly to an emergency fire-escape door lock.
Exits which are normally kept closed and locked in a building must be provided with a lock capable of being rapidly unlocked from the inside in case there is a fire or other emergency in the building. There are many kinds of locks available in the market for such purpose; these locks, however, suffer from the following disadvantages:
1) Although the lock can rapidly be unlocked from indoors, it can also easily be picked from the outside by a thief using a tool, or the lock will automatically become unlocked if the exit door is subjected to a relatively large impact force so as to cause the latch of the lock to disengage from the door strike plate by shock; the lock is thus not very effective in maintaining security.
2) Although some locks are designed such that their locking members have additional protection, most of them still have such disadvantages as: a relatively large number of parts; a complicated structure; a relatively high cost; a relatively difficult assembling procedure; and a low reliability.